Project Summary/Abstract The long-term goals of this project are to develop a high-resolution understanding of voltage-gated calcium channel (CaV) function and regulation. These molecular switches play pivotal roles in cardiac action potential propagation, neurotransmitter release, muscle contraction, calcium-dependent gene-transcription, and synaptic transmission. Calcium influx is a potent activator of intracellular signaling pathways but is toxic in excess. As a result, its entry into cells is tightly regulated. CaVs are major sources of activity-dependent calcium influx and possess a number of mechanisms that allow them to self-regulate. These mechanisms depend critically on interactions of the pore-forming subunit with cytoplasmic proteins that regulate channel activity such as the calcium sensor proteins calmodulin and CaBP1. We are investigating the molecular basis of these phenomena. Due to the extraordinary challenges in studying mammalian membrane protein structure, our efforts are directed at understanding the function of the interactions between cytoplasmic components and the calcium sensor proteins. We are pursuing a multidisciplinary approach that includes biochemical, biophysical, X-ray crystallographic, and electrophysiological measurements to dissect CaV function together with functional studies and molecular dynamics simulations to understand the structural basis of ion selectivity. Because of their important role in human physiology, CaVs are the targets for drugs with great utility for the treatment of cardiac arrhythmias, hypertension, congestive heart failure, epilepsy, and chronic pain. Thus, understanding their structures and mechanisms of action at atomic level detail should greatly assist the development of valuable therapeutic agents for a wide range of human cardiac and neurological problems.